I Do alot of Intensive Work, For Example:
-I Run Virtual Machines inside Parallels Desktop 7
-I listen to music alot
-I usually have Google Chrome With about 10 Tabs at a time
-I May do some editing once in a while

And Usually When i Run a Virtual Machine, It Slows my system Down Alot

Would a RAM Upgrade from 4 GB to 12 GB Help out alot with Running Virtual Machines and still run the host os very well?????

Many will tell you that RAM is cheap, so go ahead, whether you need it or not. If you really want to know if you'll see any performance difference for your situation, read on. Launch Activity Monitor and click the System Memory tab at the bottom to check your page outs. Page outs are cumulative since your last restart, so the best way to check is to restart your computer and track page outs under your normal workload (the apps, browser pages and documents you normally would have open). If your page outs are significant (say 1GB or more) under normal use, you may benefit from more RAM.

As a simple "1 number" check test, simply:
- Load / launch your typical heavy usage apps. Apps that you often execute the same time.
- While these many apps are minimumized, load Activity Monitor - Memory usage screen.
- If FREE Mememory value is less then 500 MB, then buy/install more RAM. Some will say that swap file size ratio is the number to focus on. And, many college/university classes focus on Swap File Size Analysys and Ratios indepth sessions as well. Many ways to "number crunch" the Swap File in/out ratio to create a yes or no recommendation. But for a simple YES or NO number check, simple look at FREE Memory value (when most common apps are loaded and minimumized). If FREE memory number is less then 500 MBs, then simply buy/install more memory in the iMac.

Note: For running parallels and multiple Apps and memory being so "low cost" these days, I would upgrade your iMac to 12 GBs of RAM. Especially if you plan to keep your iMac for many more years.

This is inaccurate. There's more to it than just free memory. Inactive memory is also available to apps. Read the link I posted to understand better.

Click to expand...

Like I said…. There is many university / college courses that focus on Page In/Page Out ratio calculations. One can obtain a Nobel prize in math and still not have enough knowledge to clearly recommend if one has enough physical RAM within their computer. Way too many other variables to take into account. For a 1 simple number to decide YES or NO, use FREE RAM value. Then (if needed), apply the in-depth Page In/Page Out math ratios that teach in Computer Science schools.

If wondering, I hold Engineering degree in Computer science and know all the BS math ratios of Page Ins/Page Outs calculations. For a simple YES or NO look to decide if a computer needs more physical RAM, I use FREE memory value with threshold of 500 MB. And yes, it works - without spitting out `over rated` math ratio formulas.

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